ul li{
    list-style: none;
}

.det{
    width: 1200px;
    margin: 0 auto;
    padding-top: 30px;
}
.thumbnail{
    height: 520px;
    
}

h3{
    text-align: center;
}
.introduce{
    padding-top:35px;
}
.introduce li{
    height: 40px;
    line-height: 30px;
    font-size: 20px;
    margin-bottom: 15px;
}

.comment{
    color: green;
}
button{
    margin-right: 20px;
}